On January 27, 1945, Soviet troops liberated Auschwitz. The date is now consecrated as International Holocaust Remembrance Day, as the world vowed never to allow murderous anti-Semitism to recur. Yet 75 years later, attacking Jews has once again become socially acceptable in many countries across the left-right ideological spectrum, and among different groups that blame Jews for their grievances and oppression.

The recent eruptions of anti-Semitism in America have awakened us to a prejudice that has long resided, in quiet ways and in many forms, in this country. And the part of it that now disguises itself as anti-Zionism hatred of the Jewish state that was established in the wake of the Holocaust as a refuge for Jews has even seemed, to some, virtuous, a sentiment they believe puts them in humanitys moral vanguard.

And anti-Semitism has returned, in part, because the general publics knowledge about the Holocaust of what exactly it was, who exactly was murdered in it, how many were killed, and how anti-Semitism spawned it has diminished. For a time, that knowledge discredited anti-Semitism and those who indulged in it. But the passing of survivors who experienced the Holocaust and could testify to it, the denial and minimization of the Holocaust, and the hijacking of the word itself to advance numerous other causes, great and small, all combined to diminish its memory. The horrifying knowledge of where anti-Semitism can lead has been, in large measure, lost in a miasma of forgetting, ignorance, denial, confusion, appropriation, and obfuscation.

As a former director of the United States Holocaust Memorial Museum, many of whose uncles, aunts, and cousins, and a grandmother, were murdered in the Holocaust; as a professor who has taught a generation of students about the memory of the Holocaust; as a psychiatrist who is well aware of humanitys repertoire of hatred and brutality; as a professor of international affairs; and as a student of Jewish history who is deeply aware of the many times masses of Jews were murdered or expelled simply because they were Jews, I watch anti-Semitisms global resurgence, so soon after the Holocaust, with alarm and foreboding. Could murderous anti-Semitism, on a large scale, resume in our time? Could never again, vowed so solemnly and so repeatedly after the Holocaust, revert to yet again?

What motivates anti-Semitism? For two millennia, the prejudice has fulfilled needs psychological, theological, national, and social that have multiplied and mutated:

Why were Jews the group that was most regularly identified, in the lands and communities theyve inhabited, as fulfilling one or more of these needs? The most likely reasons are historical and psychological: When Jews were first identified as fulfilling some of these needs, they were branded as villains. Over time, that branding was repeatedly reinforced so that Jews became the usual suspects the group that immediately came to mind when a new need arose to find explanatory villains.

So why the resurgence of anti-Semitism today?

Anti-Semitism is useful in the current moment in both Europe and America. For some on the right, it can fulfill the need for a national, religious, or ethnic agenda. And for some on the left, it can fulfill the need to establish virtue, particularly when its connected with anti-Zionism.

In Arab and Muslim lands, anti-Semitism is often expressed as both hatred of Jews and hatred of Israel, and is very frequently bolstered by Holocaust denial. Delegitimizing the Jewish state can serve as a means to reverse the humiliation, degradation, and oppression of Muslims.

In Eastern Europe, right-wing, nationalist parties have taken control, often rewriting Holocaust history, and often with the support of groups that are strongly anti-Semitic and have adopted Nazi slogans and agendas. In Western Europe, anti-Semitism is found among right-wing forces; within political parties on the left, especially in Britain; and among elements of the Muslim community.

But for now, the democracies of Western Europe are strong enough to withstand the pressure. And in America, the episodes of anti-Semitic speech and violence, though theyve greatly proliferated in the past few years, have begun to mobilize communities and governmental agencies to protect Jews from violence. This wont stop anti-Semitisms continuing growth, but it will control it. Despite a long history of bias at many levels, from academia to boardrooms, Jews in America have established themselves during the past century in every sphere of American life, and the American tradition of tolerance will remain far more powerful than its manifestations of prejudice.

So although Jews face ongoing violence, it is not of a level that will, in the foreseeable future, result in massive death. In Europe and the United States, there might be limited outbursts. Should Iran develop nuclear weapons, it could, in a moment of irrationality, launch them to try to obliterate the Jewish state, which its leaders repeatedly have vowed to destroy and which is home to nearly half of the worlds Jews; but Irans fear that it could be devastated in return by a nuclear-armed Israel would almost surely keep such a cataclysmic possibility in check. In short, despite the rise in worldwide anti-Semitism, a repeat of the Holocaust major mass murder is, though possible, unlikely in the foreseeable future.

As we mark the 75th anniversary of the liberation of Auschwitz, I wish I could be more upbeat than that. But Im not. Im a physician. I know that one can manage a chronic disease, one can treat it, one can often prevent its complications, but one can rarely cure it and one cant ever be sure that it wont become, at some point, catastrophic.